Container with controllably desensitized explosive mixtures

ABSTRACT

A composite semi-liquid system for thickening halogenated organic liquids, such as Freon 113 (a registered trademark of E. I. DuPont de Nemours &amp; Co.) to improve safety in the formulation and handling of certain highly-sensitive-to-detonation mixtures, for example, a mixture of secondary and primary explosives, or a combination of a solid sensitive oxidizer with a pyrotechnic fuel. The thickened halocarbon is used in two stages, first a selected combination of gelling agents such as Cab-O-Sil M-5 (a registered trademark of the Cabot Corporation) and Bentone 38 (a registered trademark of N. L. Industries, Inc.) is incorporated into the halocarbon and the resultant slurry is then used to desensitize the explosive by admixture. The desensitized explosive is packaged in a container which is permeable to the halocarbon vapor and this package is immersed in a vessel containing a halocarbon gel obtained by selective gellation with gellants such as Alumagel (a registered trademark of Witco Chemical Co.); this second gel provides a means for preventing a rapid escape of the liquid from the vessel if a leak occurs.

United States Patent [1 1 Picard et al.

[ 1 June 12, 1973 1 CONTAINER WITII CONTROLLABLY DESENSITIZED EXPLOSIVEMIXTURES [75] Inventors: Jean P. Picard, Morristown; H.

William Voigt, Jr., Stanhope; Lawrence W. Pell, West Orange, all of NJ.

[73] Assignee: The United States of America as represented by theSecretary of the Army, Washington, DC.

22 Filed: Nov; 17,1971

211 Appl.No.: 199,452

52 US. Cl 102/7.2, 102/58, 102/70 R,

Primary Examiner-Carl D. Quarforth Assistant Examiner-P. A. NelsonAtt0rneyI-Iarry M. Saragovitz, Edward J. Kelly, Herbert Berl et al.

[57] ABSTRACT A composite semi-liquid system for thickening halogenatedorganic liquids, such as Freon 1 13 (a registered trademark of E. l.DuPont de Nemours & Co.) to improve safety in the formulation andhandling of certain highly-sensitive-to-detonation mixtures, forexample, a mixture of secondary and primary explosives, or a combinationof a solid sensitive oxidizer with a pyrotechnic fuel. The thickenedhalocarbon is used in two stages, first a selected combination ofgelling agents such as Cab-O-Sil M-5 (a registered trademark of theCabot Corporation) and Bentone 38 (a registered trademark of N. L.Industries, Inc.) is incorporated into the halocarbon and the resultantslurry is then used to desensitize the explosive by admixture. Thedesensitized explosive is packaged in a container which is permeable tothe halocarbon vapor and this package is immersed in a vessel containinga halocarbon gel obtained by selective gellation with gellants such asAlumagel (a registered trademark of Witco Chemical Co. this second gelprovides a means for preventing a rapid escape of the liquid from thevessel if a leak occurs.

6 Claims, 2 Drawing Figures CONTAINER WITH CONTROLLABLY DESENSITIZEDEXPLOSIVE MIXTURES The invention described herein may be manufacture,used and licensed by or for the Government of the United States forgovernmental purposes without the payment to us of any royalty thereon.

BACKGROUND OF THE INVENTION For certain battlefield applications, it isdesirable to have a large number of packaged explosives, either mines ornoisemaking devices or both, dispersed in pre-' selected areas of thebattlefield. An extremely advantageous method of accomplishing this isby aircraft deployment. This air dispersal necessitates the use of alarge outer container, in which the smaller packages are disposed, priorto dispersal. Normally, after the small explosive packages are prepared,they are placed in the container at the point of preparation. Theexplosives or noisemakers are generally packed in small, vaporpermeable, packages such as fabric bags or plastic film packets.

In the past, the practice has been to render these explosives safe byimmersion in an environment of liquid halocarbon. The immersedexplosives were then packaged and shipped. These attempts to render theexplosives safe by treatment with such an environment have not beencompletely satisfactory and the danger has been compounded by thematerial handling process, which is a manual, batch type process, madenecessary, because the viscosity of the halocarbon was not sufficient tokeep the ingredients dispersed in a homogeneous manner. This type ofprocess is relatively inefficient because Freon is lost to theatmosphere and further, it is hazardous to the operators.

Attempts have been made to thicken the Freon by the use of Cab-O-Silalone, but in a number of cases this resulted in increased rather thandecreased sensitivity when the items dried out, due to surface phenomenaof the finely divided Cab-O-Sil particles in the mixture. In addition tosafety considerations, it was necessary to develop a system which woulddesensitize the explosive for a pre-determined amount of. time and thenallow the explosive to arm itself. The large container used to dispersethe small packages had to be capable of containing the explosives, inbattlefield conditions, in a desensitized, unarmed manner until theywere deployed. This was especially difficult with a liquid halocarbonsystem because of the likelihood of solvent evaporation and prematurearming of the explosive if the large container was pierced by rifle fireor shrapnel. In addition, if, any leaks developed during shipping,through accident or rough handling, the contained explosive packagesmight arm prematurely and cause serious damage. Further, a means ofpreventing impact detonation was necessary to render this type ofdeployment system feasible.

It is, therefore, an objebt of this invention to provide a halocarbongel system for controllably desensitizing sensitive-to-detonationmixtures.

A further object is to provide a halocarbon gel system for improvedsafety in loading and shipping sensitiveto-detonation mixtures.

Another object is to provide a safer method for deployingsensitive-to-detonation mixtures under battlefield conditions. i

Yet another object is to provide a safer, continuous method forpreparing and loading certain sensitive-todetonation mixtures.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same become better understood byreference to the following description, wherein it is shown that theabovementioned objects are attained and the prior art deficiencies areovercome by the use of a desensitizing slurry intimately mixed with thesensitive explosive in combination with a protective gel, disposed in alarge outer container around the packaged, desensitized explosives, toaccomplish these objects.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF A PREFERRED EMBODIMENTOur invention can best be shown in the context of the entire mun'ition.As shown in FIG. 1, the bags or envelopes 14 are filled with thedesensitized slurry mixture 16. The filled bags 14 are then loaded intoa container 10 and surrounded with the outer protective gel 12. Thecontainer 10 is provided with a controllable opening means 9 and apropulsion means 18 to deploy the filled bags 14 when desired. Inoperation, when the bags 14 are to be air deployed, the opener 9 isactivated and then the bags 14 are propelled out of the container by useof the propulsion means 18. The outer gel 12 falls away, leaving thebags 14 filled with desensitized slurry 16 to fall to the ground and armthemselves through halocarbon evaporation. This evaporation of solventmakes the item progressively more sensitive to detonation. The outerprotective gel 12 is used as an additional safety means to preventinadvertent evaporation from the inner gel 16 if the container 10 wereperforated. If such perforation did occur the outer gel 12 would form aplug to prevent evaporation. The inner slurry 16 is formulated so thatit will not form a film on drying, thus allowing halocarbon to escapethrough the bag 14. Further, the outer gel 12, while wetting the surfaceof the bag, does not form a film which will prevent evaporation of theliquid from the inner slurry 16.

In FIG. 2, the interfaces between the inner desensitized gel 16 and theouter protective gel 12 surrounding the bag 14 are shown. In operation,the bag 14 is made of vapor permeable material so that the solvent fromthe gel l4 can evaporate through it.

The desensitizing slurry is mixed with sensitive, explosive orpyrotechnic compositions. The rheological properties of this slurry aresuch that the components of the composition will remain suspended in itfor the life of the slurry. In addition, since the slurry desensitizesthe composition, thorough mixing, to insure homogeneity, can beaccomplished in relative safety. The halocarbon evaporation from thedesensitized mixture can be controlled by selecting the properthickening agents and by proper choice of bag or packaging materials.Continuous processing of separate items is made possible because of therelative safety and homogeneous condition of the mixture and because theitems can be separately weighed, if necessary, without rapid weight lossdue to halocarbon evaporation. The protective gel in which the filled,desensitized mixture packages are placed, also has rheologicalproperties which prevent it from pouring out of a vessel, through anaperture suddenly opened in the vessel. In addition, the gel can be sodesigned that its rheological properties will dissipate the impact forceof a bullet so that the desensitized mixture in the containers will notdetonate inadvertently. By the use of the composite system of ourinvention these types of explosive or noisemaker can be loaded, shippedand deployed under battlefield conditions in relative safety.

The composite system; i.e., the inner desensitizing slurry in admixturewith the explosive or pyrotechnic and the outer protective gel in thelarge container, must conform to certain parameters. The outer orprotective gel must be capable of forming a plug so that if a leak inthe container develops the gel will fill the hole to prevent the loss ofall the gel in the container. The inner desensitizing slurry must beparticulate in nature rather than a film former, to allow the item toarm through solvent evaporation. Additionally it cannot be excessivelyparticulate because the surface activity of an excessively particulatemixture increases the sensitivity of the mixture to an undesirablelevel. The interface between the outer protective gel and the surface ofthe packages must also be such that a film will not be formed on thepackages which would prevent proper evaporation by retarding vaportransmission. Since the inner desensitizing slurry must not be a filmformer to allow proper evaporation, in essence it is a thick slurryrather than a true gel. There are two requirements of this slurry; i.e.,first to wet and desensitize the explosive and second to evaporate andallow the explosive to arm; therefore, many of the parameters arelargely empirical. The slurry must effectivelymeet both criteria andtherefore it can neither irreversibly desensitize the explosive nor takemore than a practical amount of time to allow the halocarbon toevaporate. Additionally, the gellant used must be present in smallamounts so that when the liquid evaporates, the amount of gellantremaining will not adversely affect the sensitivity of the packagedmixture. Further, the amounts of gellant used must be large enough toinsure safety and controlled evaporation by forming a proper slurry.Generally, a halocarbon liquid is used for this inner desensitizingslurry because of its relative inactivity towards the sensitive mixturesand because of its high rate of evaporation. Any liquid could be usedwith our invention, however, if it did not react with or dissolve theingredients of the mixture and if it evaporated within practical timelimits.

The outer protective gel, which is a true gel, must be capable ofdissipating the impact force from a bullet or piece of shrapnel toprevent detonation of the explosive packages, it must be capable offorming a plug in holes in the container to prevent liquid evaporationand it must not form a film on the explosive packages such that theliquid would be unable to evaporate from the packages after they aredeployed. The type of gel used must conform to the criteria outlined andpreferably will be a halocarbon gel but any other gel, for example, awater gel can be used so long as it meets the above criteria.

The gelling agents that can be used with our invention are any gellingagents or thickening agents which will form a particulate slurry withthe liquid used to desensitize the explosive mixture or form aplug-forming gel with the liquid used for the outer protective gel andwhich will also form a gel that will protect the mixtures from theimpact force of bullets or shrapnel.

The particulate desensitizing slurry of our invention is formed by usinga particulate type thickening-agent in combination with a gelling agent.The particulate thickening agents used include adsorbent, inorganic,silica or alumina compounds usually of sub micron size which have asurface area of more than 100 square meters per gram, such as Cab-O-SilM-S. The gelling agents used include organic ammonium salts of acidclays such as Bentone 38, which is an organic magnesium montmorillorite,or Bentone 34, a dimethyl dioctadecyl ammonium, magnesium aluminumsilicate. The gellant used can be varied depending on the physicalproperties of the liquid to be gelled.

The particulate thickening agent gellant combination used may containratios ranging from 50 percent by weight particulate agent to 50 percentby weight gellant to 85 percent by weight particulate agent to 15percent by weight gellant. If less than 15 percent gellant is used, theslurry becomes overly sensitive due to rapid drying on the surface. Ifmore than 50 percent gellant is used, the slurry stability excessivelyretards evaporation. The preferred composition is percent particulateagent to 25 percent gellant to achieve a balance between the amount ofparticulate material present and gel stability.

The particulate size of particulate thickening agents that may be usedwith our invention will depend on their physical characteristics.Generally, the particle size can be from about 0.007 microns to 0.1microns, preferably from about 0.007 to 0.012 microns for optimumresults.

The total amount of the combination particulate thickening agent-gellantthat can be used effectively to form the desensitizing slurry of ourinvention is usually from about 1 to about 4 percent by weight of thetotal slurry, preferably about 1 to 2 percent. The minimum specified isto insure stability of the gel and the maximum to insure that theexplosive mixture will not lose its sensitivity on drying because of thepresence of too much gellant diluent.

The outer protective gel can be made from a non polar liquid and asuitable gelling agent, such as a water insoluble aluminum di-soap ofthe formula (RCOO)- Ol-l Al, wherein R is an aliphatic or alicyclichydrocarbon radical containing from seven to 22 carbon atoms.Preferably, (RCOO) represents the radical of a monobasic acid selectedfrom the group consisting of lauric, myristic, palmitic, oleic,linoleic, naphthenic, 2 ethylhexoic, stearic and mixtures thereof. Ifwater is used to form the gel, gelatin or any suitable gelling agent maybe used.

The amount of gellant used for the outer protective gel is usually fromabout 1 percent to about 4 percent of the total weight of the gel,preferably from about 1 percent to about 2 percent. If there is notenough gellant, the protective gel will not plug holes developing in thecontainer, and if there is too much gellant, the gel will be too thickand the container will be difficult to pack. Additionally, the properamount of gellant must be used to prevent film forming on the explosivepackages.

The liquid component of the inner desensitizing slurry system isgoverned by criteria of non-reactivity with the explosive, non-solvationof the explosive and an evaporation rate that will permit practicalarming or drying times for the items. Any liquid which will meet thesecriteria can be used, for example 1,1,2'trichloro-, 1,2,2trifluoroethane; 1,1 ,2,2 tetrachloro-, 1,2 difluoroethane;l,l,2,2'tetrafluoro-l,2 dibromoethane; carbon tetrachloride andtetrachloroethylene. It has been found that halocarbons of a chainlength of one or two carbon atoms containing at least one halogensubstituent are preferred, such as Freon 113 or perchloroethylene. Thesehalocarbons preferably have a boiling point between about 30 to 120C.

In the outer protective gel, the principal requirement is that thegelled liquid will form a plug to prevent subsequent leakage if thecontainer is perforated. Additionally, since the explosive packages willbe disposed in this gelled liquid, the liquid must be compatible withthe desensitizing slurry. By compatible is meant that there will be noreaction between the two liquids.

In addition, the liquid must be capable of forming a gel which willdissipate the force of bullets or shrapnel which hit the container incombat conditions and thus prevent detonation of the inner explosivepackages. Also, since the packages themselves must be able to transmitthe inner liquid vapor, the outer gel must not coat the containers sothat vapor permeation is completely restricted. Any gellable liquid,either organic or inorganic, which meets these criteria may be used. Ithas been found that the same halocarbons as used the inner gel can beused for the outer protective gel without adverse effect. Further, watercan be used as the liquid in this outer protective gel.

The solid mixtures that may be desensitized by the inner gel compose twomajor classes. First, impact sensitive pyrotechnic or noisemakingcompositions. This class is usually made up of sensitive explosives,such as mixtures of red phosphorous, potassium chlorate or perchlorateand ground glass. Any combination of a strong oxidizer, abrasive agentand pyrotechnic fuel can be used with this invention, so long as theproper criteria are followed in formulating the gels. Second, explosivemixtures composed of secondary explosives, such as RDX, and primaryexplosives, such as lead styphnate or lead azide, may be used. A numberof secondary explosives may be used in place of RDX, for example, PETNor I-IMX, may be used as well as any common secondary explosive. Theexplosive packaging material used is selected for its nonreactivity andits ability to transmit the vapor from the liquid of the desensitizingslurry. For example, cotton duck may be used as well as certain filmswhich are permeable to the liquid used in the desensitizing slurry, suchas Alathon or Tyvek polyethylene film (both names are registeredtrademarks of E. I. Du Pont de Nemours & Co.). The thickness of the filmmay be varied to achieve diverse evaporation rates.

The method and composition of this invention which may be used toproduce a safe desensitized explosive item having the propertiesdesired, is set forth in the following examples. It is, of course,understood that these examples are meant to be illustrative and notrestrictive of our invention.

EXAMPLE 1 INNER DESENSITIZING SLURRY A. A 2 percent by weight gel ofBentone, a gelling agent, in 1,1,2, trichloro-1,2,2, trifluoroethane wasprepared in the following manner. 0.8 gram of ethyl alcohol was added to2 grams of Bentone 38 and mixed to swell the gellant. The swollengellant was then added to 98 grams of rapidly agitated 1,1,2,trichloro-1,2,2 trifluoroethane using high shear dispersion equipment,at ambient temperatures. A thickened halocarbon paste of about 63 ml.volume resulted after approximately 5 minutes of agitation.

B. A 2 percent by weight slurry of Cab-O-Sil MS, a particulatethickening agent, in 1,1,2 trichloro-1,2,2- trifluoroethane was preparedby first slowly mixing 2 grams of the Cab-O-Sil with 98 grams of 1,1,2-trichloro-l,2,2; trifluoroethane to wet out the Cab-O-Sil. Then theslurry, was stirred rapidly for about 5 minutes at ambient temperaturesusing a propeller-type mixer.

C. 3 parts by weight of B was stirred into one part by weight of A atambient temperatures, using a propeller type mixer to form the innerdesensitizing slurry of 2 percent /25 Cab-O-Sil/Bentone in 1,1,2trichloro- 1,2,2 trifluoroethane.

D. To 14 grams of the slurry from C, 5 grams of potassium chlorate wasadded under agitation, then 2 grams of red phosphorous was added, andmixing continued, at ambient temperatures, until the slurry washomogeneous.

B. One gram of cut Pyrex glass was added to a small polyethylene cup anddampened with 1,1 ,2,-trichloro- 1,2,2-trifluoroethane. 3 grams of theslurry from D was dispensed volumetrically into the testing container.The slurry mixture was then dampened with 1,1,2 trichloro -1,2,2trifluoroethane and heat sealed in a cup made of 4 mil polyethylenefilm, which was closed by a rigid polyethylene disk. On drying thebomblet consisted of 35.7% by wt. potassium chlorate, 14.3 percent byweight red phosphorous, 50 percent by weight pyrex glass and 2 percentby weight gellant. The bomblet was tested for safety and proper dryingtime by the use of standard tests.

*Bentone 38 is a product marketed and trademarked by N. L. Industries,Inc. It is a magnesium montmorillonite ammonium salt modified by twomethyl and two octadecyl organic groups.

**Cab-O-Sil M-5 is a product marked and trademarked by CabotCorporation. It is a pyrogenic silica having an average particle size of0.012 microns and a surface area of 200 square meters per gram.

The polyethylene cup and disc used was made from Alathon A 3120 film (aregistered trademark of E. I. Du Pont de Nemours Co.) marketed by DuPont.

EXAMPLE 2 A number of samples with varying percentages of gellant wereobtained in the same manner as Examples 1 and 2 by varying the amount ofslurry used in the final mixture.

EXAMPLE 3 OUTER PROTECTIVE GEL Two grams of Alumagel (an aluminum disoap marketed under the trademark Alumagel by Witco Chemical Co.) wereslowly added to 98 grams of 1,1,2 trichloro 1,2,2 trifluoroethane withslow agitation at ambient temperatures. Stirring was continued, untilthe solid particles began to dissolve. The stirring was thendiscontinued and the slurry allowed to stand for about 2 hours, at whichpoint a clear colloidal gel was formed. This gel was used as a means forprotecting the items disposed in the outer container from inadvertentarming and from shock. This type of gel was tested using the proceduresdescribed herein.

EXAMPLE 4 OUTER PROTECTIVE GEL 1.5 grams of Alumagel were slowly stirredinto 98.5 grams of perchloroethylene at ambient temperatures. A clearcolloidal gel formed in about 2 minutes. This gel was used as describedin Example 2 and tested using the same procedures.

Tests were run on samples of the desensitized composition of Example 1to determine the proper gellant content for proper sensitivity coupledwith practical evaporation times. These tests are standard tests usedfor explosives and the results obtained are reported in the followingtables:

TABLE 1 EFFECT OF GEL FORMULATION AND PROCESSING ON BOMBLET MIXTURESENSITIVITY PA. Impact Sensitivity Test Value, ht, inches Freon 1 13 WetMixture Mixture Dried in Cups Material Tested 1. Control: No slurry 2%Cab-O-Sil added dry with active ingredients (I) to Freon l" 1" 1" Freonslurry active ingredients (1) added to 2% composite gellant (2) inFreon, to make up 2% gellant content, dry basis 4" 0.25 Kg wt 1 Kg wt0.25 Kgwt 1" 1" (lconsecutive explosions) Freon slurry activeingredients (1) added to 2% composite gellant (2) in Freon, to make up4% gellant content,

dry basis 6"1" (30 consecutive explosions) 4. Freon slurry activeingredients without glass added to 2% Bentone 38 gellant in Freon, tomake up 10% gellant content, dry basis 13" 3" (C) TABLE 2 CHEMICALANALYSIS OF MIXTURE SUSPENDED IN FREON 113 SLURRY Potassium Glass Totalmix tested Chlorate Red P Gellant (dry basis) Top sampling 34.37% 13.4452.19 1.9162 Bottom sampling 33.43 14.28 42.29 1.9432 Originalcomposition of mix 33.3 13.7 53 NOTES:

1. The preparation containing 4% gellant solids basis was as follows:

a. Add 2.25 grams of 2% Bentone 38 Gellant by weight in Freon to 6.75grams of Cab-O-Sil M5 silica suspended in Freon. This composite gelweighs 9 grams and contains 0.18 grams of gellant solids.

b. Blend 2.25 grams of Pyrex ground glass of 14/28 U. S. sieve meshgranulation with 1.606 grams of potassium chlorate (thru 60 mesh). Stirthis mixture into the Freon composite pre-gel Drop Weight value; Freonwet, ht. Dried Mix, ht. 2 Kg 1" 1 Kg 6" 8 oz At 1" 30 consecutive At Aexplodes violently From the results presented in Table 1, it can be seenthat the mixture of Example l is desensitized when wet and explodes whendried. The difference in sensitivity between a control mixture usingCab-O-Sil alone and the mixture of our invention is quite evident from acomparison of the height necessary to cause detonation. The mixture ofour invention requires a height of 4" vs. only 1" for the control usingthe more sensitive 0.25 kg. weight. It can also be seen that at 4 and 10percent thickening agent-gellant content the height necessary fordetonation increases substantially using the 1 kg. weight. Although themixture is less sensitive using a 4 percent content the time necessaryto dry and arm the mixture is prohibitive.

Table 2 shows that a relatively homogeneous mixture is obtained by theuse of our invention. If the mixture were suspended in liquid Freonwithout the use of Benton 38 Cab-O-Sil M5 the solid components would befound almost exclusively in the bottom layer. Additionally, a number ofrounds from M-1 and M-l6 rifles were fired at container assemblies at adistance of ft. These firings resulted in a number of direct hits. Thecontainer loaded in the manner of our invention did not detonate, itshowed a markedly enhanced insensitivity to bullet impact.

Thus, it can be seen that the use of our invention, wherein an innerdesensitizing slurry contained sensitive to detonation ingredients, isprotected by an outer protective gel to provide additional safety inshipping, handling and deployment under battle conditions, forms thebasis for an advance in the art.

We wish it to be understood that we do not desire to be limited to theexact details described, for obvious modification will occur to a personskilled in the art.

We claim:

1. A composite article of manufacture containing reversibly desensitizedexplosive composition comprising: a detonation sensitive explosivematerial, homogeneously dispersed in a non-aqueous slurry, said slurryconsisting essentially of a mixture of a first liquid componentnon-reactive with said explosive material and having a boiling pointbetween about 30 and C, and a solid component, capable of thickeningsaid first liquid component, consisting essentially of a mixture of afinely divided, adsorbent, particulate thickening agent insoluble insaid first liquid component and an inner gelling agent partially solublein said liquid component, said composition being packaged in a containerpermeable to the vapor of the liquid component of "the desensitizingslurry and wherein the container is enclosed in a protective gelcomprising a second liquid and an outer gelling agent therefore.

2. The article of manufacture, of claim 1, wherein the particulatethickening agent is a silica of sub micron size, and said inner gellingagent is an organic ammonium salt of an acid clay.

3. The article of manufacture of claim 1, wherein said composite articleis contained in a vessel impermeable to the vapor of the first liquidcomponent of both the densensitizing slurry and the outer protectivegel.

4. The article of manufacture of claim 3,'wherein said outer gellingagent is an aluminum di-soap of the formula (R COO), OH A1 and wherein Ris selected from the group consisting of aliphatic hydrocarbon radicalsof seven to 22 carbon atoms and alicyclic hydrocarbon radicals of sevento 22 carbon atoms.

5. The article of manufacture of claim 4, wherein (RCOO) is a monobasicacid radical selected from the group consisting of lauric, myristic,palmitic, oleic, linoleic, napthemic, 2-ethylhexoic, stearic, andmixtures thereof.

6. The article of manufacture of claim 3, wherein said second liquid isselected from the group consisting of 1, l, 2 trichloro-l,2,2trifluoroethane; l, l, 2, 2 tetrachloro l, 2 difluoroethane; l, l, 2, 2tetrafluoro l, 2 dibiomoethane,; carbon tetrachloride; andtetrachloroethylene.

UN TED STATES PATENT OFFICE CERTIFICATE GE QURREQTIQN Patent No.3,738,276 Dated June l2, 1973 Inventor 8 Jean P. Picard, H WilliamVoiqt, Jr. Lawrence w. Pell It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 9, lines l5-l6, delete "The first liquid component of both thedesensitizing slurry and the outer protective gel" and insert --both thefirst liquid component and the. second 'Iiquid--. Column l0. line 9,change "naphthemic" to -naohthenic--; lines 11-12, delete "said secondliquid is" and insert --both said first liquid component and said secondliquid are; line 15, change "dibiomoethane, to -dibromoethane--.

Signed and sealed this 19th day of March 1974.

(SEAL) Attest:

EDWARD M.FLETCHER',JR. C. MARSHALL DANN Attesting Officer Commissionerof Patents FORM PC4050 I USCOMM-DC 60376-P69 i U.S. GOVERNMENT PRINTINGOFFICE 2 19,9 -'3I5-33l' TINTTTD STATES PATENT oTTTcE 1 QERHMQATE GEQGRREQTWN Patent No. 39738,,276 D t d June 12, 1973 Inventofls) Jean P.Picard, H. wi11iam \loiqt, Jr., Lawrence w. Pe11 It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Co1umn 9, 1ines 15-16, de1ete "The first 1iquid component of both thedesensitizing siuvvy and the outer protective ge1" and insert --both thefirst 1iquid component and the second 1iquid-. Co1umn 10, line 9, changenaphthemic" to -naphthenic; iines 11-12, deiete "said second 1iquid is"and insert --both said first 1iquid component and said second 1iquidare-; line 15, change "dibiomoethane," to -dibromoethane--.

Signed and sealed this 19th day of March 1974.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents FORM po'wso USCOMM-DC 60376-1 69 U.S. GOVERNMENT PRINTING OFFICEI959 0-356-33,

2. The article of manufacture, of claim 1, wherein the particulatethickening agent is a silica of sub micron size, and said inner gellingagent is an organic ammonium salt of an acid clay.
 3. The article ofmanufacture of claim 1, wherein said composite article is contained in avessel impermeable to the vapor of the first liquid component of boththe densensitizing slurry and the outer protective gel.
 4. The articleof manufacture of claim 3, wherein said outer gelling agent is analuminum di-soap of the formula (R COO)2 OH Al and wherein R is selectedfrom the group consisting of aliphatic hydrocarbon radicals of seven to22 carbon atoms and alicyclic hydrocarbon radicals of seven to 22 carbonatoms.
 5. The article of manufacture of claim 4, wherein (RCOO) is amonobasic acid radical selected from the group consisting of lauric,myristic, palmitic, oleic, linoleic, napthemic, 2-ethylhexoic, stearic,and mixtures thereof.
 6. The article of manufacture of claim 3, whereinsaid second liquid is selected from the group consisting of 1, 1, 2trichloro-1,2,2 trifluoroethane; 1, 1, 2, 2 tetrachloro - 1, 2difluoroethane; 1, 1, 2, 2 tetrafluoro - 1, 2 dibiomoethane,; carbontetrachloride; and tetrachloroethylene.